"Magic," a voice replied.
Empty stood before Lucien in the next room as the doors to the room closed shut. The room seemed to be.. Outside? They were in a field of green grass which went on for miles. As soon as Lucien stepped into the field, the door behind him vanished. There were no more doors.
"Welcome," Empty said, "To your last lesson of the day here... I will not be teaching you basics that you already know. I will be teaching you that which you have not yet learned.. That which you shall use in combat."
After he explained these words, Empty's form began to shift. It took the form of KiaB, the Anrufe leader. Empty was imitating KiaB for the purpose of the lesson. He knew that Lucien would soon face the Anrufe, among other foes. KiaB was the leader of that organization, so it made sense that Empty would choose his form to imitate out of all others within the Anrufe.
A pink goo of some sorts appeared on the ground and started to weave itself around the ankles of Lucien.